High-voltage fuse construction



Feb. 21, 1950 R. R. PITTMAN 2,498,575

HIGH-VOLTAGE FUSE CONSTRUCTION Filed Aug. 4, 1947 INVENTOR Patented Feb. 21, 1950 UN IT ED STATES PATENT. O FFICE HIGH-VOLTAGE" FUSECONSTRUCTION Ralph ll.. Pittman, North Little Rock, Ark,

Application August 4, 1947, Serial No. 765,927"

5 Claims-- (Cl.- 200-113-)- This invention relatesi generall to fusesiorelectric circuits; and more specifically to a fuse construction suitableforause'on circuits operating onvoltages commonly classified astransmission line voltages; e. g; 66 kv; and greater. 7,

The objects- 0f the inventioninclude the provision of a relativelyinexpensive fuse'construction adapted for highlvolta ge circuits whichis at a the: same time 1 effective for the interruption of'currentoverva wide range extending-from a few amperes tovseveralirthousanduamperes; the provisionof o a. fuse 1 construction: 1of: the above mentioned abilityv which .is particularly adapted toapplicationii'to /circuits"provided witha grounded source; the provisionof a fuse construction iembodyin'g'itwoexpulsion fusebarrels in series.-arrangement zfiiniz which a predetermined sequence-of :meltinglo'f thefusible elements ofthe fuse: linkwithin;thesrespective barrels is causedto occur in: responsetopassageoi a'predet'ermined current: throughthefuse-slink and" the provision ofa construction' utili'zing theconducting dis charge: gas attending: operation to efiectcertaindefinite and favorable-alteration of the fault cur rent to'beinterrupted by the fuse. Other objects will be'ob'vious from thedescription tofollow; or pointed outth'ereinllr In the?accompanyingdrawing, FigL 1 is-a side elevati'onal viewiof a fuse constructionconstructed in accordance: with the presentinvention Fig: 2 is an: endelevational view; Fig. 3 is a diagrammatic 1 sketch illustrating' :the'application of the invention toia single phase circuit; Fig; 4 is afragmentary view or" a portion of one of the :fuse ba'r relszofi the devicewith' a portion broken-awayto show the contained.-fusible element; andFig. 5 is a 'similar 'view oi a portion of 'the'other fuse barrel.

It is Well known that a fixed -b'ore expulsion fusecmayi be readily!constructed as arr effective circuit interrupting devi'ce forany circuitvoltage if 'the' currerit to be interrupted is not too greattciburstath'e: expulsion barrel :from internal pressure;ior.* is not toosmall-to'cause" sufficient gas generation tolextinguish th'e' areplaying within the barrel that "is, within well defined limits ofcurrent to beinterrupted; the expulsion fuse is an "efficient'. device.However, as a protective device for the highivoltage sidev oftransformers operating 'at'transmission line voltages the expul. sionfuse has not been" satisfactory: becausev the current to beinterruptedfmay vary; from'ia few amperes. due-to a fault on the" lowvoltage side, to a high current value equal to thevlin'e-toground faultvcurrent, often severalthousand -.am'-

peres." Sincethe line-to-groundfault current is relatively constant atany .pointon a transmission system} an arrangement assuring that thiscurrent would pass through an expulsion barrel re gardless of thecurrent causingthe fusingof a fusibleelement'of the fuse link solves thevariable current problem and results' insanl eflicientland inexpensiveinterrupting device; The manner in whichathe' pre'sent invention solvesthe problem above described, which 'has existed from the firsttime:expulsion fuseswere: used on high voltage circuits; will. be clear--from: the' following description.

Referring to Fig: 1 of the drawing, a metal base H], which incommon'pra'ctice is grounded as-indicated symbolically at 39,lhas-rigidly secured thereto', as by welding, anoutwardly extending.conducting member H. Mounted-at the respective ends of the base [0- arethe insulator stacks l2 and [3, by means'of the bolts 25. At the top ofstack 12 is mounted, by'means' of the bolts I 8, the source terminal 14and the upwardly extending source fuse barrel mount IS; the latterbeingformed ofconductingmaterial and disposedin conductive relation withthe source terminal [4: Similarly, atthetop of the stack [3 is mounted;by'meansofthe bolts 19, the 1 load terminal [5 and the-upwardlyextending load fuse barrel mount I 1; the latterbeing also formed ofconducting material and: mounted in conductive relation with theloadterminal [5.

The source expulsion fuse barrel ZZ hasrigidly fastened thereto at'itsupper end the metal'ferrule 34, and'is rigidly securedto the inclinedportion 2il 'of the source'fuse mount lfi'by'th'e U bolts 24 in such aposition that the barrel extends downwardly and'outwardly from the upperend of the fuse mount l6 and ispointed toward an outwardly extend'edportion: of the: conducting member ll. Similarly, the load expulsionfuse barrel 23 is provided withitheferrule33 at the upper end'thereof,and the latter clampedto the inclined portion 21 of the load fus'e'mountWhy the U bolts24in-su'ch a position that the load fuse barrel extendsdownwardly and outwardly from the upper end of the fuse mount l'l'i'nthe direction toward and spaced from both the outwardly extendingconducting member ll andthe lower end of the source fuse barrel fl."Preferabl the fuse barrelsare arranged, as shown, so that thelongitudina1= axis of each if" produced intersects the conducting memberll at'a common point. The fuse barrels are open at each end, and formedfrom material -commonl used :in the construction of expulsion iuses,suches hardfiber;orother material capable of producing a gas blast whenan arc occurs within the barrel.

The fuse link 26 has one end thereof connected to the source fuse mount[6 at the terminal 30, extending first downwardly through the sourcefuse barrel 22, thence across the space separating the respective lowerends of the fuse barrels to the lower end of the load fuse barrel 23,thence upwardly therethrough to the terminal 29 at the upper end of thefuse mount H, and thereby electrically connecting the terminal 14 to theterminal l through the fuse link 26. Two longitudinally spaced fusibleelements 2'! and 28 are pro vided in the fuse link 26, as shown indetail in Figs. 4 and 5, the higher current element 21 being containedby the source fuse barrel 22, and the lower current element by the loadfuse barrel 23, Under certain conditions it maybe desirable that thebore 43 of the load fuse barrel be smaller than the bore 44 of thesource fuse barrel, although this is not essential to correct operationof the device under other conditions. Also, under certain conditions,more particularly those in which load current is of substantialmagnitude, the fusible elements may approach each other as to fusingcurrent, or even equal in this respect.

In situations where load currents are too small to provide the desiredexpulsion of the fuse link 26 from the load fuse barrel 23, a fuse linkextractor 3! is mounted on the lower ferrule 32 and arranged tocontinuousl urge the fuse link in endwise direction out of the bore ofthe barrel. The fuse extractor 3! is formed of a strip of a resilientmaterial one end of which is rigidly secured to the ferrule 32 by thescrews 35, and the other end hooked over the fuse link 26 when the stripis deformed, to urge the fuse link in endwise direction away from thefuse barrel.

Fig. 5 illustrates diagrammatically an application of the invention to asingle phase circuit, although it is clear that it may be similarlyemployed in a three phase circuit. The high voltage winding of thesource transformer 36 is grounded at 38, and the other end of the highvoltage winding connected through the source conductor 3! to the sourceend of the fuse construction. In like manner, the high voltage windingof the load transformer 41 is connected to ground at 12, and the loadconductor 40 extended to the load side of the fuse construction.

Assuming that a fault occur-s on the low voltage winding of thetransformer it 'while the fuse link 26 is in the position illustrated inFig. l, the relatively small excess current as limited by the impedanceof the transformer fuses the low amperage element 28 within the loadfuse barrel 23. The fuse extractor 3! urges the fuse link 26 out of theload fuse barrel 23, and in falling, the fuse link 26 contacts thegrounded fuse link interceptor l i having moved to the position shown bythe dashed line of Fig. 1. Since the source transformer is alsoconnected to ground, full line-to-ground shirt circuit current nowpasses through the fusible element 21 of the source fuse tube 22, fusingthe fusible element and causing efiective expulsion action within thelatter for interrupting the circuit. An are, if any exists within theload fuse barrel 23 prior to contact of the fuse 2G with the groundedinterceptor II, is of course instantly extinguished by such contact,since ground voltage is then impressed across both terminals of sucharc. A portion of the fuse link 26 may take the position shown in Fig.3, or may fall to the ground, this matter being of no importance in theoperation of the device.

In the event of a direct load conductor-to ground fault, both fusibleelements will be fused at substantially the same time, and in certainsituations the conducting gas expelled from the fuse barrels will effectthe desired source conductor-to-ground fault current through the sourcefuse barrel 22 to assure circuit interruption therein. It will also beclear that it is not essential that the conducting member H bephysically contacted by the fuse link 26; it is sufiicient thatconducting gas attending expulsion action bridge the space between thelower end of the source fuse tube 22 and the grounded member II, andfurther, this gas may originate in either of the fuse barrels.

It may be observed that the construction herein not only assuressufficient fault current to effect efiicient circuit interruption, butalso assures that both of the fusible elements will be fused and therebyprovides a definite open circuit in air between the lower ends of thefuse barrels after operation. The latter feature becomes an importantconsideration when the fuse construction is applied to polyphasecircuits, because of the possible feed-back through a high voltagewinding of a load transformer connected to an unaffected phaseconductor.

I claim as my invention:

1. A high voltage fuse construction for use between a grounded sourceand a load; comprising a metal base, a grounded conducting memberrigidly mounted thereon and extending laterally therefrom, spacedinsulators carried by said base and extending upwardly therefrom, sourceand load terminals mounted respectively on said spaced insulators,upwardlyextending fuse barrel mounts fastened at their respective lowerends to each of said spaced insulators in conductive relationship withthe source and load terminals respectively, expulsion fuse barrelsmounted on the respective upper ends of said fuse barrel mounts andextending outwardly and downwardly therefrom in spaced relationship andeach in the direction toward and spaced from said grounded member, therespective lower ends of said fuse barrels being open, and the groundedmember positioned in the path of gas expelled from the respective openends of said expulsion fuse barrels, and a fuse link extending seriallythrough said expulsion fuse barrels and electrically connecting' saidfuse barrel mounts, said fuse link being provided with twolongitudinally spaced fusible elements, one of said fusible elementsbeing positioned within one fuse barrel and the other of said fusibleelements being positioned within the other fuse barrel.

2. Th construction recited in claim 1, characterized by said fusibleelements having unlike fusing characteristics.

.3. A high voltage fuse construction for use between a grounded sourceand a load; comprising a metal base, a grounded conducting memberrigidly mounted thereon and extending outwardly therefrom, spacedinsulators carried by said base and extending upwardly therefrom, sourceand load terminals mounted respectively on said spaced insulators,upwardly extending fuse barrel mounts fastened at their respective lowerends to each of said spaced insulators in conductive relationship withthe source and load terminals respectively, expulsion type source andload fuse barrels mounted on the respective upper ends of said fusebarrel mounts and extending downwardly and outwardly therefrom in spacedrelationship, each of saidfuse barrels being open at their respectivelower ends and pointed toward said load fuse barrel and a source fusibleelement i located within said source fuse barrel, said load fusibleelement being adapted to fuse upon passage of a predetermined loadcurrent therethrough, and said source fusible element being adapted toremain unfused upon passage of said predetermined load currenttherethrough and to fuse upon passage of a source-to-ground currenttherethrough which is greater than said predetermined load current, saidgrounded member being positioned in the path of gas expelled from therespective lower ends of said expulsion fuse barrels.

4. In a high voltage fuse construction, a con ducting base, insulatingmeans thereon supporting spaced terminals, spaced downwardly extendingopen-ended expulsion fuse barrels mounted on said insulating means andso positioned that the direction of gas discharge from each barrelconverges at a common point, a fuse link embodying one fusible elementwithin one barrel and another fusible element within the other barrel,said fuse link extending serially through said expulsion fuse barrelsand electrically connecting said spaced terminals, a grounded conductingmember rigidly secured to said base and extending to said common point,and a fuse link extractor associated with said fuse link and arranged toeject a portion of said fuse link from one of said barrels when thefusible element therein fuses, said grounded member being positioned inthe path of the ejected portion of said fuse link.

5. In a high voltage fuse construction, a conducting base, insulatingmeans thereon supporting spaced terminals, spaced downwardly extendingopen-ended expulsion fuse barrels mounted on said insulating means andso positioned that gas discharge from each barrel converges at a commonpoint, a fuse link embodying one fusible element within one barrel andanother fusible element within the other barrel, said one fusibleelement fusing at a predetermined current less than the fusing currentof said another fusible element, said fuse link extending seriallythrough said expulsion fuse barrels and electrically connecting saidspaced terminals, and a grounded conducting member rigidly secured tosaid base and extending to said common point.

RALPH R. PITTMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,928,625 Kyle Oct. 3, 19332,390,670 steinmayer Dec. 11, 1945

